linux-kernel - Re: sys_execve leaking rbp/rbx/r12-15 to the new process?

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Date:	Sat, 4 Apr 2015 16:04:17 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>
Subject: Re: sys_execve leaking rbp/rbx/r12-15 to the new process?


* Denys Vlasenko <dvlasenk@...hat.com> wrote:

> We can do this instead:
> 
> ENTRY(stub_execve)
>         CFI_STARTPROC
>         call	sys_execve
> 	testl	%eax, %eax
> 	jz	1f
> 	ret
> 1:      addq	$8, %rsp
> 	xorl	%ebx, %ebx    // maybe create a macro for zeroing these
> 	xorl	%ebp, %ebp    //
> 	xorl	%r12d, %r12d  //
> 	xorl	%r13d, %r13d  //
> 	xorl	%r14d, %r14d  //
> 	xorl	%r15d, %r15d  //

Yeah, call it ZERO_EXTRA_REGS or so.

> Any reason we should not do this change?

Not that I can see - lets try it.

Thanks,

	Ingo
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